The effect of verapamil on potassium fluxes in canine cardiac purkinje fibres

Electrophysiological studies of verapamil on isolated cardiac tissue show its effects to occur during Phase 2 and Phase 4 of the cardiac action potential and to be a result of blocking the slow inward Ca 2+ current. It is important to know if verapamil effects the transmembrane movement of ions other than Ca 2+ . By studying uptake and efflux of 42 K by canine cardiac Purkinje fibres in the presence and absence of verapamil (1.1 × 10 −6 M–4.4 × 10 −6 M). it was found that the drug inhibits both 42 K uptake (15%) and efflux (30%).